The invention relates generally to a rack or creel for receiving spools on which thread material is wound and, more particularly to a spool rack having interconnected tubular carrying and connecting struts on which are arranged spool holders.
Spool racks having interconnected carrying and connecting struts that define a standable frame that carries a plurality of spool holders are used extensively as so-called side racks for circular knitting machines. This type of spool rack is also used, however, for other applications involving feeding threads, wires or similar filament-form material to a common processing or treatment location.
For example, a spool rack for a circular knitting machine is disclosed in DE GBM 7 338 340. This spool rack is constructed from individual elements which are joined together into a round or flat rack. The individual elements comprising the rack consist of vertical carrying bars and horizontal connecting bars each having a tubular construction with a rectangular cross-section. Slip-on holders for the spools are arranged on the carrying bars and corresponding thread-guide elements are provided to define the desired thread running paths. Since such spool racks are necessarily very bulky structures, the individual elements are generally supplied disassembled and are put together at the end-use location. The DE GBM 7 338 340 reference does not describe in detail how the individual bars are connected together. However, in practice, the individual bars are typically assembled using a variety of different connectors, including, for example, plug connectors and pipe clips.
As a result of the ever increasing weight of the spools used on such racks, considerable mechanical demands are placed on the spool rack, particularly in relation to the stability of the rack and the strength of the connections of the individual struts of the rack. Moreover, as will be appreciated, assembly of the spool rack should be simple so that untrained personnel can carry it out. Finally, the connectors used to assemble the struts should have a minimum of easy-to-handle individual parts.
Accordingly, in view of the foregoing, a general object of the present invention is to provide a spool rack which has a mechanically sound design and is easy to assemble.
In accordance with these and other objects of the present invention, a spool rack is provided in which the individual struts of the rack are assembled together at particular connection points using respective connecting assemblies that include a connecting element that is slidable into a first tubular strut and a threaded socket that is slidable into a second mating tubular strut. The connecting element includes a pressure transmitting portion arranged to engage the inner wall of the corresponding first strut. A holding portion is connected with the pressure transmitting portion for releasably fixing the connecting element in the strut. When assembled, the two struts are joined together by a screw bolt which is supported by the pressure transmitting portion, and extends through a passage bore in the wall of the first strut and is received in the threaded socket.
A very stable, firm connection is produced by the combination of the threaded socket that is inserted into the second strut and the pressure transmitting portion that is inserted into the first strut for supporting the screw bolt. Because the pressure transmitting portion can be detachably fixed in the strut by the holding portion before the screw bolt is inserted, the assembly of the spool rack is substantially easier. The pressure transmitting portions only have to be inserted into the particular struts until they are in the correct position at the respective connection points, where they are fixed in position by the holding portions. The carrying and connecting struts then can be screwed together easily at the connecting points.
The connecting element can be constructed of a plastic material as the connecting element does not include any force-absorbing threads, parts or the like that would impose special demands on the material strength. Instead, it is only necessary that the connecting element absorb the pressure force resulting from the tightening of the screw bolt and transfer the force to the inner wall of the strut. To achieve this, in the case of struts in the form of cylindrical tubes, the pressure transmitting portion should include a substantially cylindrical bearing surface for engaging the inner wall of the strut. As is the case with the entire connecting element, including the pressure transmitting portion, the bearing surface does not impose particular high demands on the required manufacturing precision. Similarly, the form and diameter tolerance of the inner surface of the tubular strut does not have to be manufactured with high precision. Accordingly, for example, welded tubes can also be used directly as the struts, as the present invention is in no way restricted to the use of cylindrical tubes as the struts. To mention only a few examples, the tubular struts can be constructed in the form of polygonal profiled tubes or the like having rectangular or square cross section. The holding portion of the connecting element can comprise a holding member in the form a cylindrical lug added to the pressure transmitting portion that positively cooperates with, or fits within, the passage bore in the strut or as a part which engages a projection on the inner wall of the strut. As will be appreciated, the invention is not restricted to these examples. When the connecting element is inserted into the strut, the holding portion enables the connecting element to be fixed with respect to the passage bore at the particular connecting point in a simple manner. The fixing of the connecting element is facilitated if the holding portion has an elastic supporting portion connected with the pressure transmitting portion which allows the pressure transmitting portion to be pressed against the inner wall of the strut. This construction enables the pressure transmitting portion to be resiliently positioned, with respect to for example the passage bore, at the connection point during the insertion of the pressure transmitting portion into the strut.
The elastic supporting portion includes, in one advantageous embodiment, an essentially hairpin-shaped spring part, which is either molded as one piece onto the pressure transmitting portion or is joined with the pressure transmitting portion as a separate part, for example in the form of a metal spring leaf. Alternatively, the elastic supporting portion can comprise, for example, a compression spring which is operable between the pressure transmitting portion and the inner wall of the strut. The hair pin shaped construction of the spring part is particularly suitable when the connecting element is constructed as a one-piece plastic part.
The pressure transmitting portion and the supporting portion suitably include, in each case, a continuous bore for the screw bolt with the two bores being aligned with one another. In order to facilitate the insertion of the connecting element into the tubular strut, the connecting element can be constructed such that at least the elastic supporting portion has elements which allow a tool, for example tongs, to be applied so as to press the supporting portion against the pressure transmitting portion as described in greater detail below.
Finally, in order to permit some adjustability of the struts joined with one another at the connection points, the passage bore can alternatively be formed as a cylindrical or a longitudinal hole in the longitudinal or circumferential direction of the strut. In this context, it should be noted that the use of the connecting element also enables struts to be connected at the connection points, not only with other struts, but also with a wall or the like, in which a corresponding threaded socket is provided.
These and other features and advantages of the invention will be more readily apparent upon reading the following description of a preferred exemplary embodiment of the invention and upon reference to the accompanying drawings wherein: